Various types of environmental condition sensors have been known. For instance, temperature sensors for sensing temperatures includes thermistors, thermocouples or platinum-wire heat-responsive resistors. When these temperature sensors per se are used as temperature sensors for cooking equipment, they are exposed to smoke, unburned gases such as CO, or carbon vapor so that oil films or soot adhere to the surfaces of temperature sensors and consequently the characteristics of temperature sensors vary. Therefore, temperature sensors have previously been covered with covers such as metallic gauze or the like to prevent the adhesion of oil films or soot. However, these contaminants adhere to the cover itself so that the temperature sensor is isolated from the environmental atmosphere and consequently erratic signals are generated.